The present invention relates to radar systems, and more particularly, to the development of high resolution range (HRR) radar target profiles.
Many present day radar systems combine frequency-stepped transmit waveforms with Fourier-type receiver decoding in order to develop HRR target profiles. In other words, transmit waveform pulses of incrementally increasing frequency are sent out in the direction of a target, and reflected return signals are received and then Fourier-transformed to produce coefficients indicating individual target scatters. The resolution of the resulting target profiles is inversely proportional to the frequency range, or Agile Bandwidth, of the discrete frequency-stepped pulses. In conventional non-FFT radar systems, resolution is proportional to pulse width, and because very short pulses can be difficult to generate, FFT HRR systems are superior to conventional non-FFT systems in certain contexts.
The Fourier-based systems are premised on the fact that the frequency-stepping process is equivalent to encoding an inverse-Fourier transform on the outgoing transmit signal. Such systems are described in, for example, "Generation of High Resolution Radar Range Profiles and Range Profile Auto-Correlation Functions Using Stepped-Frequency Pulse Trains" (Project Report No. ESD-TR-84-046), by T. H. Einstein, Massachusetts Institute of Technology, Lincoln Laboratory, Lexington, Mass., Oct. 18, 1994. While Fourier-based HRR systems do provide advantages over traditional coarse-range systems as noted above, the Fourier transform process is computationally intensive, requiring on the order of Nlog.sub.2 N complex multiply-and-accumulate operations for an N-point transform. As a result, Fourier-based systems are limited in terms of speed, and therefore in terms of radar range resolution, and may be unsuitable in modern applications requiring high speed and accuracy. Thus, there is a need for a radar system in which HRR profiles can be generated more quickly and with finer resolution as compared to known systems.